You’ll need to be on the latest 2019.08.18.267044774 build to see the change, but it may be a while before everyone gets the option as the dark theme option is an additional server-side flag that needs to be enabled. The interface is similar to what we’ve seen from other Google apps: you get three options for themes, including Light, Dark, and System default. The theme option itself is listed at the top in the general settings, and the dark mode has a dark gray color scheme with red accent colors.

Don’t see the theme option just yet? Make sure you’re on the latest build, and wait for the server-side change to go live.